The Ejection SiteF-1ll Crew Module Escape and Survival SystemsThis document comes from a self-study text and is primarily
an introduction. Text and graphics
have been edited to improve readability, but content is unchanged.

The development of the high-speed F-111 aircraft caused the need for an improved egress system.
The ejectable crew module was designed to meet this need. The system provides maximum protection
for the crewmembers throughout the aircraft performance envelope and includes capabilities for
safe ejections at maximum speed and altitude as well as at zero altitude and 50 knots indicated
airspeed (KIAS). The module is self-righting, watertight, has flotation provisions, and provides
protection for the crewmembers from environmental hazards met on land or water. A side-by-side
crew arrangement facilitates safe and effective performance and allows crewmembers to work
together and aid one another in performing mission tasks while still maintaining their forward
visibility which is an important factor in high-speed, low-level flights.

In this unit we will look at the many systems that make up the crew module. We will break these
systems down into components, tie these components together and trace the ejection sequence.

Crew Module operation. Ejection is initiated by actuating either of the ejection
initiators. The ejection initiators detonate the SMDC which provides a simultanious transfer
medium for the the crew module. Each end of the SMDC lines has has a stainless steel
booster tip (fig 11). Propagation from one booster tip to another is accomplished by the
impact of the shrapnel formed by fragmentation of the thin stainless steel booster tip
sheathing. The detonation rate of the SMDC is 20,000 to 25,000 feet per second with
an associated pressure front of 3 to 4 million psi.

The secondary controls guillotine is actuated to sever secondary control
cables and the normal oxygen hose, the blade antenna leads guillotine is actuated
to sever the coaxial antenna leads, and the leading edge antenna
leads guillotine is actuated to sever the leading edge antenna leads in the wing.

The emergency oxygen system is activated.

The propagation of SMDC continues to the mechanical explosive interrupt which allows
or stops the propagation as the crewmember desires. If the unit is closedm then propagation
is stopped. The chaff dispenser and emergency radio beacon are not activated. If the unit is
open, then propagation continues and activates the emergency radio beacon and a 3.0 second
time-delay initiator. The time-delay initiator gives the crew module
time to clear the aircraft before it fires, actuating the chaff dispenser.

The 0.35-second time-delay initiator is activated. This time-delay initiator delays firing of
the rocket motor and severance of the crew module until steps a through e have occurred. Severance.
After an interval of 0.35 second, the time-delay initiator fires, causing the following events:

The 0.15-second time-delay initiator is activated delaying firing of the
stabilization/brake parachute catapult until after the crew module has left
the aircraft.

The rocket motor is ignited.

The backup SMDC to the guillotines, emergency oxygen system, and chaff dispenser is detonated.
This portion of the system is provided in the event of failure of the SMDC when ejection is initiated.

The FLSC is detonated, severing the crew module mating devices from the aircraft and the
stabilization/brake parachute severable cover from the crew module. At the same moment the FLSC
severs the crew module from the aircraft, the 1.6 and 4.4-second time-delay initiators are activated.
At this point, the dual-mode, q-actuated selector determines which route the SMDC takes. The q-actuated
selector senses aircraft speed and determines whether the aircraft speed is above or below 300 knots so that it can select the appropriate time delay.

Separation. When the module is completely severed from the aircraft, the rocket propels the crew
module up and away from the aircraft. After a 0.15-second delay, the stabilization/brake parachute
catapult is fired and deploys the parachute.

At speeds below 300 knots, the dual-mode, q-actuated selector prevents propagation to the rocket
motor upper nozzle diaphragm FLSC assembly, and activates a 1.0-second delay initiator and DTA
lines going to the select interrupt valve. At this point, the select interrupt valve is repositioned
allowing the stabilization/brake parachute cutters to release the stabilization/brake parachute during
the low-mode ejection. The 1-second delay allows the crew module to clear the aircraft and stabilize in flight, before the recovery parachute is deployed. After a 1-second delay, the initiator will fire and activate the barostat lock initiator. The barostat lock initiator, when fired, activates the recovery system and releases the stabilization/brake parachute.

At ejection speeds above 300 knots, the dual-mode, q-actuated selector prevents propagation to the
1.0-second delay initiator and DTA lines leading to the select/interrupt valve and allows
propagation to activate the 0.15-second time delay initiator. Since the selector interrupt
is not repositioned during high-speed ejections, the stabilization/brake parachute remains
attached to the module throughout the ejection sequence. Firing of the 0.15-second time-delay
initiator
continues SMDC propagation to the rocket motor upper nozzle FLSC assembly to sever the diaphragm.
Because the barostat lock initiator cannot be activated through the dual-mode, q-actuated selector
above ejection speeds of 300 knots, a 1.6-second time-delay initiator is provided. This initiator
delays SMDC propagation to the g-sensor initiator for 1.6 seconds after rocket motor ignition.
Once the 1.6-second time delay has elapsed, the initiator activates the g-sensor initiator. After
the forward speed of the crew module slows down to approximately 2.2 g's, the g-sensor initiator
fires, activating the barostat lock initiator.

Another explosive train, with a 4.4-second time-delay initiator, is provided to back up both the
dual-mode, q-actuated selector and the g-sensor initiator.